N′-[(E)-4-Benzyloxy-2-hydroxybenzylidene]-4-nitrobenzohydrazide dimethylformamide monosolvate

The title compound, C21H17N3O5·C3H7NO, exists in an E conformation with respect to the azomethine double bond of the hydrazide molecule. This molecule contains an intramolecular O—H⋯N hydrogen bond, while an intermolecular N—H⋯O hydrogen bond links the hydrazide to the formamide molecule of solvation. Nonclassical C—H⋯O intermolecular hydrogen bonds build up a supramolecular architecture, together with two C—H⋯π interactions and a weak π–π interaction, with a centroid–centroid distance of 3.650 (13) Å.

The title compound, C 21 H 17 N 3 O 5 ÁC 3 H 7 NO, exists in an E conformation with respect to the azomethine double bond of the hydrazide molecule. This molecule contains an intramolecular O-HÁ Á ÁN hydrogen bond, while an intermolecular N-HÁ Á ÁO hydrogen bond links the hydrazide to the formamide molecule of solvation. Nonclassical C-HÁ Á ÁO intermolecular hydrogen bonds build up a supramolecular architecture, together with two C-HÁ Á Á interactions and a weakinteraction, with a centroid-centroid distance of 3.650 (13) Å .
The compound crystallizes in monoclinic space group P2 1 /c. This molecule adopts an E configuration ( Fig.1) with respect to C14-N1 bond with torsional angles of 177.93 (18)°. The title compound exists in amido form with C15-O3 bond length of 1.217 (3) Å, which is very close to C═O bond length of a similar reported nitrobenzohydrazide compound (Joseph et al., 2012). The aromatic ring (C1-C6) of the compound forms dihedral angles between the other two aromatic rings (C8-C13 and C16-C21) with angles of 67.63 (12) and 61.58 (12)° respectively. There are one classical N2-H2′···O6 and three non-classical C-H···O intermolecular hydrogen bonds (Fig. 2) present in the molecular system with D···A distances of 2.810 (3), 3.167 (3), 3.448 (3) and 3.206 (3) Å (Table 1) respectively. These intermolecular hydrogen bonds chain the molecules along c axis. Moreover, two C-H···π interactions between the H atoms attached at the C12 and C17 atoms and the corresponding aromatic ring C1-C6 of the neighbouring molecules with H···π distances of 3.673 (2) and 3.630 (3) Å respectively, also support the hydrogen bonding to form a one-dimensional layer along c axis. This supramolecular network is augmented by a weak π-π interaction ( Fig. 2) between the phenyl rings (C8-C13 and C16-C21) of the molecules with a centroid-centroid distance of 3.650 (13) Å by interconnecting the molecules along b axis.
Packing of molecules is predominantly favored by the classical intermolecular hydrogen bonding and C-H···π interactions. Other short ring interactions are very weak as they correspond to their centroid-centroid distances greater than 4 Å. Intramolecular classical hydrogen bond is also observed in the molecular system (Table 1). Fig. 3 shows the packing diagram of the title compound along c axis.

Experimental
The title compound was prepared by adapting a reported procedure (Mathew & Kurup, 2011;Despaigne et al., 2009). A methanolic solution of 4-nitrobenzohydrazide (0.181 g, 1 mmol) was added to a solution of 4-(benzyloxy)-2-hydroxybenzldehyde (0.228 g, 1 mmol) in ethanol and the reaction mixture was refluxed for 5 h after adding a few drops of dilute sulfuric acid. On cooling yellow colored crystals were collected, washed with few drops of methanol, and dried over P 4 O 10 in vacuo. Single crystals of the title compound suitable for X-ray analysis were obtained by recrystallization from a mixture of ethanol and dimethylformamide (1:

Refinement
All H atoms on C were placed in calculated positions, guided by difference maps, with C-H bond distances 0.93-0.97 Å.
H atoms were assigned as U iso =1.2Ueq (1.5 for Me). N2-H2′ and O2-H2O H atoms were located from difference maps and restrained using DFIX instructions. Omitted owing to bad disagreement was the reflection (2 6 2).

Figure 1
ORTEP view of the title compound drawn with 50% probability displacement ellipsoids for the non-H atoms.

Figure 2
Hydrogen-bonding, C-H···π and π-π interactions present in the crystal structure of C 21 H 17 N 3 O 5. C 3 H 7 NO.  Packing diagram of the compound along c axis.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.40 e Å −3 Δρ min = −0.22 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0078 (15) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.